The prior art is replete with devices for use in dispensing an additive into a toilet cistern and a bowl thereof, which require no moving parts to facilitate their action. These range from relatively simple devices, such as those in which a block of additive material is held within a container having an opening into which the water in the cistern enters and dissolves or disperses the additive and by diffusion through the opening produces a concentration of additive in the cistern water, to relatively complex devices having air locks, baffles and the like to facilitate controlled delivery of additives.
An example of the latter mentioned type is disclosed in UK patent application No. GB2114623-A. Although dispensers of the latter type have the ability to provide a substantially constant concentration and volume of additive to the cistern and bowl, their complex design and resultant relative high costs generally have made these devices unattractive in large scale consumer use.
Similarly, whilst the relatively simple dispensers of the first mentioned kind have achieved wide consumer acceptance, because the additive is present in the cistern water, when a toilet is flushed, a substantial proportion of the additive will be flushed to waste. As the additive is generally required to produce an effect in the water of the toilet bowl, the amount of additive not remaining in the bowl after flushing is clearly wasted. Moreover, in most cases, the presence of additive in the cistern water during quiescent periods serves no useful purpose. Further, by allowing the relatively large volume of cistern water to remain in continuous contact with the additive during quiescent periods, this results generally in increasing concentration of additive in the cistern water with time.
To minimize the amount of additive wasted, additives have been incorporated into various solid matrices that allow the additive to be dissolved or dispersed in the cistern water at a controlled rate. Whilst this approach may achieve some reduction in the maximum concentration of additive in the cistern water, nevertheless, during prolonged quiescent periods, the concentration of additive in the cistern water will become excessive. More importantly, this approach will have no effect on the proportion of additive that is flushed to waste.